F21 Workstation Hardware Requirements

[Owen Taylor]

On Mon, 2014-09-01 at 12:43 -0600, Pete Travis wrote:

> Virtualization opens an entirely different context for hardware
> requirements. QXL for guests hosted on my low power i3 utility server
> run gnome-shell quite acceptably; my i7 workstation brings that up to
> near-native for modern integrated graphics.  Traditional cirrus type
> graphics deliver a wholly unusable experience on the same hardware.
> QXL isn't a magic bullet, though; on hosts with older hardware,
> performance definitely degrades.  I don't have a lot of experience
> with VMWare or vbox stacks, but I assume there is a spectrum of
> unacceptable to adequate to excellent there as well.

qxl actually is effectively just software rendering when applied to
GNOME 3- it may be that there's something _worse_ than just software
rendering going on with the cirrus driver - I'm not sure why it was so
much worse for you.

In terms of performance with qxl, I don't immediately have numbers in a
VM, but testing some of the tests that run on perf.gnome.org (*) with
LIBGL_ALWAYS_SOFTWARE=1, which triggers the same drawing paths as you
get with qxl, I see:

# Time to redraw frame with a maximized application update
applicationRedrawTime 2.9ms => 82.4ms
# Time to redraw the main view, full screen
mainViewRedrawTime 3.2ms => 21.8ms
# Time to redraw the overview, full screen, 5 windows
overviewRedrawTime 5.4ms => 37.0ms

This is with a 2560x1440 resolution - at a smaller resolution for the
VM, the situation won't be as bad, but it's not really near native.
Given development time to put into it, the applicationRedrawTime number
can definitely be improved - there's a lot of extra copying of pixels
around that isn't needed.

My experience with VBox is that the 3D support (which is off by default)
has too many bugs when used with GNOME Shell to enable; software
rendering performance seems similar to with KVM/qxl.

The general expectation for current behavior is that in a VM Fedora will
be responsive, but not smooth. Many animations will automatically be
turned off, which helps at making the lack of smoothness not be glaring.

The main extra requirement that you need to use Fedora Workstation in a
VM is memory - trying to run Fedora Workstation in a VM with less than
4GB on the host is futile; I've never seen that work. Typically,
machines with 4GB of memory have enough CPU to do OK with the graphics. 

- Owen

(*) You can run these tests on F21 with:
  
    gnome-shell-perf-tool --replace --perf=hwtest --extra-filter=Gedit
   
   the numbers above have some not-yet-landed performance work for
   background redraws.